High Idle
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
If the above is true...then a truck must have a PTO trans installed in order for the high idle feature to function. Just like you suggested earlier.
Posting Guru
Joined: Apr 2010
Posts: 1,112
Likes: 0
From: South Shore, MA
Great info. The sensor you are talking about is the TSS. That sensor on non-PTO models is 37mm long. PTO units have a sensor that is a little over 18mm in length....probably for the reason you describe. Sorta makes sense to me....that must be why I had to drive my wife's truck before the high idle would work after I reinstalled the PCM.
If the above is true...then a truck must have a PTO trans installed in order for the high idle feature to function. Just like you suggested earlier.
If the above is true...then a truck must have a PTO trans installed in order for the high idle feature to function. Just like you suggested earlier.
The thing that keeps me thinking is, what if someone was running a serpentine acc. that required 'high idle' to operate??
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
I tried a test. Two of my trucks are model year 2000. One with a PTO and other without. the high idle worked on the PTO truck while the other truck did not work. I swapped PCMs (thinking the programming was in the PCM). It didn't work. In fact, neither truck had fast idle. I drove about half a mile in the PTO truck and the fast idle began working again. I then drove around a little bit in the non-PTO truck (with the PCM from the truck with a previously working high idle switch) and the high idle would not work. I swapped the PCMs back to their original trucks and the only truck with high idle was the truck with the PTO trans.
This pretty much proves to me that the PCM can tell when a PTO trans is installed. I dont think there is any practical way to fool the PCM into thinking a PTO trans is installed.
Elder User
Joined: Feb 2006
Posts: 765
Likes: 1
From: Eastern Ohio
It actually has to be a PTO transmission. The PCM can tell the difference. There appears to be a different tooth count or some way for the TSS to sense when a PTO trans is installed. That is why the truck must be driven before the high idle will work.
I tried a test. Two of my trucks are model year 2000. One with a PTO and other without. the high idle worked on the PTO truck while the other truck did not work. I swapped PCMs (thinking the programming was in the PCM). It didn't work. In fact, neither truck had fast idle. I drove about half a mile in the PTO truck and the fast idle began working again. I then drove around a little bit in the non-PTO truck (with the PCM from the truck with a previously working high idle switch) and the high idle would not work. I swapped the PCMs back to their original trucks and the only truck with high idle was the truck with the PTO trans.
This pretty much proves to me that the PCM can tell when a PTO trans is installed. I dont think there is any practical way to fool the PCM into thinking a PTO trans is installed.
I tried a test. Two of my trucks are model year 2000. One with a PTO and other without. the high idle worked on the PTO truck while the other truck did not work. I swapped PCMs (thinking the programming was in the PCM). It didn't work. In fact, neither truck had fast idle. I drove about half a mile in the PTO truck and the fast idle began working again. I then drove around a little bit in the non-PTO truck (with the PCM from the truck with a previously working high idle switch) and the high idle would not work. I swapped the PCMs back to their original trucks and the only truck with high idle was the truck with the PTO trans.
This pretty much proves to me that the PCM can tell when a PTO trans is installed. I dont think there is any practical way to fool the PCM into thinking a PTO trans is installed.
Tried to rep you, buy I'm in jail.
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Joined: Jan 2011
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From: Puget Sound
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Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
There are plenty of 4x4 transmissions without the PTO feature. From my observations, there are 4 different versions of 4R100 transmissions for the 7.3 engine.
However, some rebuild kits do offer an coast clutch upgrade where the PTO clutches are installed in a non-PTO transmission. This helps beef up the transmission for exhaust brake use or for other extreme applications. Unfortunately, this still does nothing for the high idle feature. My F450 has an 4R100 built by ATS with the PTO coast clutch upgrade but the transmission case is the standard type so the high idle feature will not work. On that truck I accomplish high idle via AIC or the PHP chip.
An easy way to spot a PTO trans is by looking for the access plate on the side of the case or the physical presence of the PTO drive itself.
- 2WD non-PTO
- 4WD non-PTO
- 2WD PTO
- 4WD PTO
However, some rebuild kits do offer an coast clutch upgrade where the PTO clutches are installed in a non-PTO transmission. This helps beef up the transmission for exhaust brake use or for other extreme applications. Unfortunately, this still does nothing for the high idle feature. My F450 has an 4R100 built by ATS with the PTO coast clutch upgrade but the transmission case is the standard type so the high idle feature will not work. On that truck I accomplish high idle via AIC or the PHP chip.
An easy way to spot a PTO trans is by looking for the access plate on the side of the case or the physical presence of the PTO drive itself.
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
Matt,
Is your 4R100 a PTO model? If so, then you will need to reset the PCM before the high idle feature will work. I can walk you though that process if you would like. First you need to see if you have an access plate on the side of the case.
Is your 4R100 a PTO model? If so, then you will need to reset the PCM before the high idle feature will work. I can walk you though that process if you would like. First you need to see if you have an access plate on the side of the case.